1. Field of the Invention
The present invention relates to a liquid electrophotographic printer, and more particularly, to a development apparatus for a liquid electrophotographic printer having a cleaning device for effectively removing a developer liquid sticking to a squeegee roller.
2. Description of the Related Art
An electrophotographic printer employs a developer liquid in which a toner is mixed with a volatile liquid carrier.
Referring to FIG. 1 illustrating an example of a general liquid electrophotographic printer, a photoreceptor belt 110 circulates on an endless track around first, second and third rollers 121, 122 and 123. The first roller 121 is a backup roller for pressing the photoreceptor belt 110 against a transfer roller 124 for transferring a toner image formed on the photoreceptor belt 110 to a recording sheet 126, the second roller 122 is a steering roller for preventing meandering by adjusting the torsion force of the photoreceptor belt 110, and the third roller 123 is a driving roller driven by a driving motor (not shown) for circulating the photoreceptor belt 110.
The transfer roller 124 presses against a pressing roller 125 with a constant pressure, and the toner image on the transfer roller 124 is transferred to the recording sheet 126 carried between the transfer roller 124 and the pressing roller 125. A charging station 135 for electrically initializing the photosensitive surface of the photoreceptor belt 110 by charging the photoreceptor belt is provided in the vicinity of the photoreceptor belt 110 between the first roller 121 and the second roller 122. Laser scanning units 130 for forming latent electrostatic images by irradiating laser beams onto the photoreceptor belt 110, and development devices 140 for developing the latent electrostatic images into toner images by applying a developer liquid of a predetermined color to the latent electrostatic images, are alternately provided in the section of the photoreceptor belt 110 between the second roller 122 and the third roller 123.
The toner image passes over the third roller 123 and is dried by a drying roller 171. The drying roller 171 absorbs the liquid carrier remaining on the photoreceptor belt 110 and the carrier is evaporated by a heat roller 172 in contact with the drying roller 171.
Referring to FIG. 2, a colored developer liquid 148 is contained in a case of the development device 140, and a development roller 143, and first and second squeegee rollers 146 and 147 are disposed in the moving direction of the photoreceptor belt 110 above the developer liquid 148. The development roller 143 applies the developer liquid 148 to the photosensitive surface of the photoreceptor belt 110. The developer liquid 148 is supplied between the development roller 143 and the photoreceptor belt 110 by a developer liquid supplier 145. A cleaning roller 144 installed under the development roller 143 cleans the surface of the development roller 143. The first and second squeegee rollers 146 and 147 remove excess developer liquid remaining after the latent electrostatic image is developed. The developer liquid sticking to the first and second squeegee rollers 146 and 147 is separated by blades 151a and 151b in contact with the surfaces of the first and second squeegee rollers 146 and 147.
Referring to FIGS. 3 and 4, the development roller 143 is spaced apart from the photoreceptor belt 110 by a predetermined distance and rotates in the same direction as the photoreceptor belt 110 travels, to apply the developer liquid 148 supplied therebetween to the photoreceptor belt 110. The developer liquid 148a sticking to the photoreceptor belt 110 forms a development region 115, which is the same width as the development roller 143 and is squeegeed by the first squeegee roller 146 rotating in the traveling direction of the photoreceptor belt 110. A thin-film like toner image 148d corresponding to the latent electrostatic image is formed on the development region 115 by the excess developer liquid due to the squeegeeing by the first squeegee roller 146. As the first squeegee roller 146 descends and then rotates opposite to the traveling direction of the photoreceptor belt 110, the developer liquid sticking to the first squeegee roller 146 is separate from the first squeegee roller 146 by the blade 151a in contact with the first squeegee roller 146 and drips down into the case 141.
Wrap-around developer liquid 148c is pushed to both edges 148b of the photoreceptor belt 110, outside the development region 115, when squeegeed by the first squeegee roller 146, and then removed by the second squeegee roller 147 in contact with the edges 148b of the photoreceptor belt 110. The second squeegee roller 147 rotates opposite to the traveling direction of the photoreceptor belt 110 to remove the wrap-around developer liquid 148c by contact with the photoreceptor belt 110. The wrap-around developer liquid 148c sticking to the second squeegee roller 147 is separated from the second squeegee roller 147 by the blade 151b in contact with the surface of the second squeegee roller 147.
The blades 151a and 151b are made of a soft elastomeric material but have a shorter life than other components of the development apparatus. When worn or damaged, blades 151a and 151b cannot serve their purpose but may damage the surface of the squeegee rollers 146 and 147. Thus, after the blades 151a and 151b are used for a certain period, they must be replaced with new ones.
However, since the blades 151a and 151b are coupled to brackets 152a and 152b, respectively, and the internal structures of the development devices 140 for accommodating the blades 151a and 151b and the brackets 152a and 152b are complex, it is very difficult and time consuming for a user to detach the blades 151a and 151b. Since it is not possible to replace only the blades in some cases, the whole development apparatus must be replaced, which is expensive.